Electrocoagulation involves the coagulation of bleeding tissue by the application of electrical energy to the tissue. Conductive gas electrocoagulation involves conducting electrical energy to the tissue as arcs in ionized conductive pathways in a flowing stream of inert gas. A more complete description of conductive gas electrocoagulation is available in U.S. Pat. Nos. 4,781,175, 4,901,719, and 4,901,720, all assigned to the assignee of the present invention.
During conductive gas electrocoagulation, the conductive gas jet is typically delivered to the tissue by a handpiece that the surgeon manipulates. Gas and electrical energy are delivered from an electrosurgical apparatus to a transfer electrode located within an electrically insulated gas nozzle located within the handpiece. The gas flows through the nozzle and over the electrode where it is ionized by the electrical energy applied to the electrode. Electrical energy is transferred from the electrode as arcs in conductive pathways in the gas flowing to the tissue.
It is desirable that the transfer electrode be fixedly mounted and centered within the gas nozzle, to achieve the best energy transfer and electrical insulating characteristics. Furthermore, the energy transfer characteristics are enhanced by exposing a maximum amount of the electrode to the flow of gas within the nozzle. As a result of these and other considerations, prior art handpieces have utilized complex structures to center the electrode within the nozzle.
Prior art handpieces, as typified by U.S. Pat. Nos. 4,781,175 and 4,901,719, have required the construction of a one piece ceramic molded nozzle and electrode assembly to retain and center the electrode within the nozzle. The molded assembly is formed by centering the electrode within a mold, inserting ceramic material into the mold, and allowing the ceramic material to harden around the electrode. Once completed, the nozzle and electrode assembly is secured to the remainder of the electrosurgical handpiece. Although effective, these prior art nozzle and electrode assemblies are somewhat costly to manufacture, due to the costs of the insert molding used to form the assembly.
The nozzle and electrode assembly described in U.S. patent application Ser. No. 592,810, also assigned to the assignee of the present invention, is a unitary, molded assembly which is slip fit within a gas supply tubing at the handpiece. This type of assembly reduces the cost of a conductive gas electrocoagulation handpiece because of its convenient use of the gas supply tubing to achieve some of the functionality of the handpiece. However, the structure which creates the nozzle and supports the electrode is still a single molded unit.
Alternatives to molding the nozzle and electrode supporting structure around the electrode involve the use of centering devices to locate the electrode within a length of prefabricated ceramic tubing which serves as the nozzle. This type of support is generally located at a midpoint of the electrode and is intended to function in conjunction with another support at the rear of the electrode to maintain the electrode in the center of the nozzle. U.S. Pat. No. 4,040,426 is an example of such an arrangement. As described in this patent, the support member supports the electrode only along a limited length of the electrode, and thus the rear end of the electrode requires additional support within the handpiece body. One difficulty with this type of arrangement is maintaining the electrode in the centered position. Movement of either the middle or rear support can shift the position of the electrode and adversely affect its operating characteristics. Furthermore, although this support arrangement is simple in concept, it can be difficult to employ practically because of difficulty in assembling the nozzle, electrode and handpiece to obtain support for the rear end of the electrode.
It is with regard to this background information that the improvements available from the present invention have evolved.